Humankind cannot gain anything without first giving something in return. To obtain, something of equal value must be lost. That is Alchemy's First Law of Equivalent Exchange.
"Alchemy: the science of understanding the structure of matter, breaking it down, then reconstructing it as something else. It can even make gold from lead. But alchemy is a science so it must follow the natural laws: to create, something of equal value must be lost. This is the principal of equivalent exchange. But I learned that night that some things cannot be measured on a simple scale. My brother and I knew the laws of science, of equivalent exchange. The game required sacrifice, that something had to be taken from us, but we thought there was nothing more we could loose....We were wrong."
People cannot gain anything without sacrificing something. You must present something of equal value in order to gain something. That is the principle of equivalent exchange in alchemy.
"In the early days, we believed that to be the onetruth in the world." -Alphonse Elric
It can be written two ways; for example, 1:10 or 1/10. Equivalent ratios (which are, in effect, equivalent fractions) are two ratios that express the same relationship between numbers. We can create equivalent ratios by multiplying or dividing both the numerator and denominator of a given ratio by the same number.
This equation does not give us the value of the unknown factor but gives us a equivalent ratio between two unknowns.
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.